Engine mounts may be used to attach engines to vehicle frames or other suitable structural vehicle elements. However, the engine and/or vehicle may generate vibrations during operation. Therefore, hydraulic dampening engine mounts have been developed to attenuate engine vibrations during vehicle operation. Hydraulic engine mounts may provide several configurations, enabling the dampening provided by the mount to be adapted for different operating conditions. For example, while driving on a smooth road at highway speeds the vehicle may shake and vibrate unless engine mounts having a high dynamic stiffness and damping are used to mount the engine on the frame. On the other hand, soft engine mounts having low dynamic stiffness are required to provide good isolation of the engine during engine idle conditions. As such, hydraulic engine mounts may have a first configuration for idle operation dampening and a second configuration for motive engine operation dampening.
A typical hydraulic mount includes a first fluid chamber (e.g., pumping chamber) enclosed by a first elastomeric member, wherein the first fluid chamber includes one or more fluid tracks (e.g., orifice tracks) opening to the chamber and extending to a second fluid chamber or reservoir that is typically bounded by a flexible second elastomeric member (e.g., diaphragm). The second fluid chamber is typically located on the opposite side of a partitioning structure from the pumping chamber. During compression, fluid is pressurized in the first fluid chamber and flows through the one or more fluid tracks to the reservoir. During rebound, fluid is drawn back to the first fluid chamber from the second fluid chamber. Mount dynamic stiffness and damping performance are thus determined, for example, by characteristics such as first fluid chamber geometry, chamber wall material, and the one or more fluid track properties.
Typical hydraulic mounts may further include an elastomer type decoupler that aids in isolating high frequency, low displacement vibrations. Modification of the properties of the decoupler may thus result in changing the level of damping provided by the engine mount. Toward this end, U.S. Pat. No. 6,361,031 B1 teaches a decoupling diaphragm, one side of which is exposed to the fluid in the first fluid chamber, and the other side of which is exposed to the pressure level in a control cavity. During normal operation, the control cavity is vented to atmosphere, and the mount functions as a typical hydraulic mount. However, a solenoid actuator may be actuated to trap air in the control cavity, which acts as an air spring thus resisting movement of the decoupling diaphragm. As such, resistance to deflection of the decoupling diaphragm is greater than that provided when the control cavity is communicated to atmosphere, but less than that provided when the decoupling diaphragm is seated against a surface. However, the inventors herein have recognized potential issues with such a method. For example, the use of a solenoid actuated valve increases the cost and complexity of the engine mount and requires the use of active control. Another approach taught by U.S. Pat. No. 6,361,031 B1 includes the use of a vacuum actuated valve in place of a solenoid actuated valve to trap air in the cavity. However, the use of a vacuum actuated valve suffers from the same issues, namely the requirement for active control over the trapping of air within the cavity to create an air spring.
Thus, the inventors have developed systems and methods to at least partially address the above issues. In one example, a method is provided comprising, in a first condition, evacuating (e.g., applying a second pressure) a vacuum chamber housed within a partitioning structure of a hydraulic engine mount such that a first fluid track (e.g., idle track) and a second fluid track (e.g., ride track) are opened in parallel and such that a decoupler element is maintained seated against the partitioning structure; and in a second condition, applying atmospheric pressure (e.g., applying a first pressure) to the vacuum chamber such that the first fluid track is closed, the second fluid track is maintained open, and air is passively trapped underneath the decoupler.
As one example, the application of the first pressure passively traps air under the decoupler by closing a vacuum-actuated valve (e.g., second vacuum actuated valve) and directing the flow of air through a first air passage to a second air passage via a one way check valve, the second air passage in fluid communication with the decoupler and the closed second vacuum-actuated valve, and wherein the first and second air passages and one way check valve housed within the partitioning structure. In this way, air may be passively introduced underneath the decoupler depending on engine operating conditions, the stiffness of the introduced air pocket or air spring adding to the stiffness of the decoupler, without the need for additional active control.
As one example, the first condition may comprise selectively applying the second pressure (e.g., vacuum) to the vacuum chamber under conditions wherein vehicle speeds are less than or equal to a predetermined speed, such a condition referred to as an idle mode, and wherein the second condition may comprise selectively applying the first pressure to the vacuum chamber under conditions wherein vehicle speeds are greater than a predetermined speed, such a condition referred to as an ride mode.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.